After ITV executives were introduced to their new boss at a meeting in the network centre last Wednesday, there was a collective intake of breath. The mood of incredulity did not fade as Simon Shaps, the Granada chief executive with whom they have wrestled over programmes and budgets, and who spent most of his summer pinned to the canvas over such flops as Celebrity Wrestling, sat down and introduced his plans.

"Hey, this is a new world. I'm going to roll up my sleeves, get on with it," he told MediaGuardian later.

Whispers had been circulating throughout the previous day, reaching a climax at an ITN party at the Royal Opera House on Tuesday evening - one of several such events as ITV celebrated its 50th birthday. The non-appearance of Mick Desmond, chief executive of the ITV broadcasting division, and a beaming smile on the face of Shaps were the only clues most needed.

Desmond duly followed head of sales Graham Duff out of the ITV door. Finance director Henry Staunton will also leave once a replacement is found. And no one expects it to end there. Note was taken of the brief appearance of director of programmes Nigel Pickard at the staff party, at which chief executive Charles Allen mingled with the throng in a characteristically spangly jacket. Pickard is widely expected to leave within the next few weeks with a generous payoff, after Shaps was installed with a near-identical job, but above him in the ITV hierachy.

The boardroom reshuffle came after a tough few months. Despite Allen's success in wooing regulators recently, ITV1 is struggling. Partly due to a desperate summer and a shaky daytime relaunch, ratings are down 6% so far this year, commercial impacts down 8%. Allen has been telling the City for months that ITV is unconcerned about the fall in ITV1 ratings as long as its overall share holds up, but his management shakeup suggests even he does not believe that any more. And by parachuting Shaps into the top creative job, the boss has made it clear where he feels the blame lies. As far as Allen was concerned it was Pickard and his colleagues at network centre that should shoulder the blame for the travails of ITV1 over the past year, rather than Granada, the inhouse production outfit responsible for 63% of ITV's programmes.

Through the fug of 50th birthday hangovers, the inhabitants of ITV network centre at Gray's Inn Road in London were speculating on who else might leave. Those who worked at Granada in Manchester well remember Shaps's arrival in 2001, following a two-year sojourn in charge of the doomed Broadband division, and all the departures and appointments that followed. Nick Elliott, the veteran drama controller, and Mark Sharman, the recently appointed controller of sport, were said to be among the more vocal opponents. Elliott wondered aloud how the new faces would tackle the central problem facing ITV - getting decent programmes on screen. And those in charge of departments that have contributed to the ratings slide, including head of daytime Nick Thorogood and controller of factual Bridget Boseley, will be feeling vulnerable.

Shaps makes no secret of the fact there are personnel changes on the horizon. "I am very likely to bring in new people, that there are nine and a half people commissioning ITV's entire programming is almost certainly too few," he says.

The key charge levelled at Allen is that he has shuffled his pack instead of dealing a new hand. Critics say that his shakeup fails to address the fact that ITV is still "half pregnant" - Granada, or ITV Production as it will now also be known, will still make shows for other broadcasters. And despite Shaps's move from Granada, detractors do not believe it will do much to ease the inherent tension between the various heads of the ITV Hydra. They claim Allen has failed to grapple with the question of what to do with Granada/ITV Production long term.

The changes also put Shaps and Ian McCulloch, his former colleague who developed the Fast Forward strategy from which the plan flowed, in the spotlght. Daring duo

To his detractors, Shaps is the archetypal political animal who has "risen without trace". To his fans, he has the mixture of commercial nous, charm and programming expertise required to solve the network centre's dysfunctional relationship with its production arm once and for all. Making the sort of noises aimed at pleasing the City, Shaps said that from now on the focus would be entirely on pleasing ITV's key customers - its advertisers.

McCulloch, the new commercial diretor, is a fearsome negotiator and cost cutter who came up through the sales route, and has worked closely with Shaps down the years. The pair crossed paths at LWT in the early 1980s and went on to work together at Granada. They are company men through and through, and McCulloch repeats the advertiser-focused mantra. "We've been confused. Companies work best around one objective, rather than multiple ones."

"Advertisers buy access to a trusted relationship with the viewer. We have to understand the viewers and have a good relationship with them. And know how to access the most valuable ones with the right programmes," he says. "Now we have to get the entire organisation aligned to that."

Shaps says he is going to review the schedule from top to bottom: "I am going to look overall at the performance, agree a strategy, the schedule architecture." To the undoubted chagrin of ITV News editor-in-chief David Mannion, all bets for the 10.30pm News remaining at a fixed time must be off.

Shaps says one enduring priority is to look after the "relatively few numbers of shows delivering a very high proportion of commercial impacts, Coronation Street, Emmerdale, This Morning, The Bill. We must add in newer shows, we must invent new banker shows and event television".

Despite transferring across from running ITV's production company, and being a campaigner against the statutory independent quota, Shaps now insists: "I will draw a line under that relationship." On hearing which the big independents are likely to arch an eyebrow, fold their arms and wait for proof. Money money money

ITV is currently reliant on advertising revenue, having twice failed to ride the pay-TV boom, although Jeff Henry's consumer division will become increasingly important in working out how to make money from mobile and broadband. The decision to elevate McCulloch - he was sent to Harvard business school last Easter - is based on his vision that fresh ways of making money have to be found. The most valuable eyeballs for advertisers are ABC1s and 16-34s, but it is no longer that simple.

McCulloch says: "We are still doing work on which viewers are the most valuable. The current Barb system doesn't help. It would put Michael Howard and Mick Jagger in the same classification . . . We need to know who are heavy users, say of iPods, who buys lots of cars. We are looking at a wide range of research, to try and segment audiences by age, sex and class."

None of which will come as music to the ears of those who have spent the last few weeks looking nostalgically at ITV's heyday. Shaps insists that this approach will bear fruit. "It won't be painting by numbers, this isn't a world where we go to people and ask them what do they want us to make. But we are trying to produce a more commercial schedule."

The rich irony is that advertisers are already grumbling about the personnel changes. "It is a disgrace, Allen has no idea what he is doing," says one senior advertising industry insider. And the City is none too impressed either. On Wednesday morning, speculation on the dealing floors was that Allen's departure was about to be announced. Shares rose 3% - then lost all their gains when the City was offered the heads of Desmond and Staunton instead.

Leigh Webb, analyst at Panmure Gordon, said Charles Allen was "effectively passing the buck" by ousting Desmond. And Anthony de Larrinaga, analyst at SG Securities, said "I don't get the feeling that this is some big structural change in approach. You had a leaking ship with two captains fighting over which way to steer. That could not go on but why the appointment of Simon Shaps will change the key issue - the stuff they have been commissioning - I don't know."

If Allen's latest attempt to impress the judges fails, there can be little doubt as to whose head will be next on the block.